Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Greenhouse gases, anthropogenic aerosols and the uptake and storage of excess heat in the climate system (#237)

Damien Irving 1 , Susan Wijffels 2 , John Church 3
  1. CSIRO, Hobart, Tasmania, Australia
  2. Woods Hole Oceanographic Institution, Woods Hole, MA
  3. Climate Change Research Centre, University of New South Wales, Sydney

Human activities have substantially altered the radiative properties of the atmosphere, giving rise to a planetary energy imbalance. The largest contributor to this imbalance is well-mixed greenhouse gases (GHGs), which are partially offset by poorly-mixed (and thus northern mid-latitude dominated) anthropogenic aerosols (AAs). To isolate the effects of GHGs and AAs, we analyse data from the CMIP5 historical (i.e. all natural and anthropogenic forcing) and single forcing (GHG-only and AA-only) experiments. We find that over the duration of the historical experiment (1861-2005), global excess heat uptake at the top of the atmosphere and ocean surface occurs almost exclusively in the Southern Hemisphere (SH). The influence of GHGs is similar for both hemispheres, with AAs completely offsetting that influence in the Northern Hemisphere (NH) but having little impact in the SH. The interplay between GHG and AA forcing also explains key features within each hemisphere, with AAs offsetting GHG-forced local maxima in ocean heat uptake in the NH but not SH. Despite this AA-induced SH-bias in surface heat uptake, we find no hemispheric bias in historical oceanic storage of excess heat after accounting for ocean volume. These results provide potential new insights into the fundamental mechanisms behind many aspects of both simulated and observed regional climate change.